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Sorry, I was mistaken. It doesn’t have a mass airflow sensor. It’s a calculated value based on throttle position and load. But back to the o2 sensor, they normally start out low voltage then come up as the sensor warms up, then it oscillates between about 250 to 850 millivolts at idle. Looking at the graph it does show some oscillation, but then returns to the high side of the graph. See if the sensor looks ok physically (not damaged or covered in oil), and inspect the wire harness near the sensor to see if there is any chafing.
Hi Dave, Is the lower right gauge air flow and intake air temp? If it is airflow at 12 to 14 that would be really high for idle. Should be around 8 or 9. Maybe you’ve got a dirty mass air flow sensor.
Hi, It sounds like your on the right track there:
“So in looking at the fuel trims, I leads me to the idea that the engine thinks it is running rich and is backing off of the fuel trims”
The engine (computer) “sees” the fuel mixture as being very rich via the O2 sensor high voltage signal. Normally the voltage should oscillate between 200 and 800 millivolts. You need to determine if it’s really running rich, or is the O2 sensor sending bad data. I’m guessing it’s not running too rich because of the way it stalls. Try comparing the O2 senor readings when the engine is cold opposed to when when it’s fully warmed up.
Is it just the belt that wobbles or is it the pulley? Hows the tensioner pulley? Might want to replace that if you haven’t already.
If you end up having to replace the cylinder head, I’ve had really good experience with a place called cylinder heads international in texas. You can order online and they ship it to you. I’ve used them a number of times. They do great work.
I wouldn’t expect there to be any codes. When you crank the engine does it sound normal or does it kinda free wheel?
Hi there, Your short term fuel trim is a little bit high. Can you monitor the pre cat o2 sensor during cold start warmup? Maybe the sensor is tired and sending false info to the PCM until it warms up good, making the engine run too rich and skippy for a minute or two. Does it high idle ok when cold? See if you can make the engine smooth out if you give it a little throttle.
Your fuel pressure is probably ok because it starts and runs ok. You probably don’t need a smoke test, though you might have a clogged vacuum hose (how old is that pcv valve?). Don’t worry about timing because it runs ok otherwise, but if you have any kind of exhaust leak near the o2 sensor that will definitely mess things up.It might not be getting enough idle air flow. Try cleaning the carbon buildup around the throttle body plate.
Hi, It sounds like maybe the #1 cylinder fuel injector is leaking fuel when the engine is off, fouling the spark plug.
Ok, let’s assume that the fuel pressure is ok. Going back to the computer data, two things stand out. The short term fuel trim is way lean at minus 18, meaning the engine computer is leaning out the fuel mixture, and the calculated load seems high at 28 percent. If the engine was cold I would expect to see it at 28% idling, but warm engine should be about half of that. The engine computer is compensating for what it sees as a rich condition, based on sensor data – high load with low air flow. Try cleaning the air flow sensor and fix that broken vacuum hose if you haven’t already. After you do that I would expect it to start hard one more time. After it runs a bit see if it stops and restarts like it should.
Hi, Try fixing the line yuo said was broken by the air flow sensor. It sounds like you might have a fuel pressure regulator problem (by not holding fuel pressure). Does that broken line go to the fuel pressure regulator?
Just a thought. That open line could also be affecting your STFT (short term fuel trim) wich is way off.
